Explain to me Electromagnetic Induction, EMF to be exact...

[QueenZ]

Hello, I am struggling to understand how electricity is generated in an AC generator... I know that there is a coil of wire and a magnet, and both of them have their own magnetic fields and as the magnet moves into the coil's magnetic field, it causes electrons to move in that coil. Well if that is right, then why is there no current flowing if the circuit is open? It only seems to be the case if the circuit is closed. I think it's called Electromotive force but how does it work? Does it literally PUSH the electrons? what difference does it make if we have a closed or an open circuit? If it PUSHES the electrons even in an open circuit then the wire would get hot and it would burn, no?

To illustrate this, I've put together 2 pictures, in which we have a closed circuit (we have current flowing) and in the other one we have the same thing but with an open circuit (I guess there's no current flowing there? why?).

Are the electrons moving or not in the second picture? why?

 

[telectrix]

imagine a closed loop of pipe with water in it, with a pump. as the pipe is a loop, water will flow, pushed by the pump. if you then add resistance ( in the case of a pipe, by restricting the flow) the flow will be reduced. if you add an infinite resistance, i.e. block the pipe, no flow.

 

[QueenZ]

imagine a closed loop of pipe with water in it, with a pump. as the pipe is a loop, water will flow, pushed by the pump. if you then add resistance ( in the case of a pipe, by restricting the flow) the flow will be reduced. if you add an infinite resistance, i.e. block the pipe, no flow.

yes, but in the case of electricity, especially in AC current, why can't the electrons go back and forth until the circuit break?

 

[telectrix]

because, without an actual current path, there is no potential difference anywhere, so no current flow. try a 12v battery and a lamp circuit. the lamp will light. you will have +12v on 1 side of the lamp and 0v on the other. now take the - lead off the battery, and you will find there's +12v on both sides of the lamp

 

[Knobhead]

He has got to be a wind up merchant!

 

[QueenZ]

He has got to be a wind up merchant!

LOL. No I'm just trying to get my mind around this concept....

 

[Silly Sausage]

QueenZ, did you look at that website I sent you a link to the other day?

 

[QueenZ]

QueenZ, did you look at that website I sent you a link to the other day?

Which one? I'm pretty sure I did.... but this EMF thing is kinda hard to get....

 

[Silly Sausage]

Which one? I'm pretty sure I did.... but this EMF thing is kinda hard to get....

Generation, EMF etc are things that you can't really explain easily (for me anyway) in a few lines on a forum. You need to do more reading then ask more specific questions.

 

[QueenZ]

OK, here's the part I don't get. How does a magnet moving through a coil wire create a potential difference in the wires??

 

[QueenZ]

Why doesn't the wire then burn up? in an open circuit if the electrons are going back and forth to create the pd?

 

[Knobhead]

Read the ebook Practical electricity; a laboratory and lecture course for first year students of electrical engineering, based on the international definitions of the electrical units by W. E. (William Edward) Ayrton

 

[Darkwood]

Like other members who have a deeper curiosity, you have to learn the basics first and accept the outcome for what it is, going into the quantum world of how a moving magnetic field induces a voltage into a copper wire is like trying to swim the channel before you've swam a length at your local swimming pool, you got the background knowledge but you lack the understanding of how complex this question is.
An ill leave you with the what im trying to express, in A.C. electrons don't move anywhere, you are taught they do to make the concept easier to learn; as trying to explain the propagation of the electromgnetic field is a very hard subject, but if you push a magnet through a set of coils you use the magnetic field to push the electron field in the copper (not the electrons), as the field strengthens then weakens you get a wave effect in this field or to you and me a Pushing force (voltage). Its like a stick of wood is your magnetic field and if you push it through the water it creates a bow wave in front of it although not exactly the same it creates a visual context that might agree with you.

 

[QueenZ]

Like other members who have a deeper curiosity, you have to learn the basics first and accept the outcome for what it is, going into the quantum world of how a moving magnetic field induces a voltage into a copper wire is like trying to swim the channel before you've swam a length at your local swimming pool, you got the background knowledge but you lack the understanding of how complex this question is.
An ill leave you with the what im trying to express, in A.C. electrons don't move anywhere, you are taught they do to make the concept easier to learn; as trying to explain the propagation of the electromgnetic field is a very hard subject, but if you push a magnet through a set of coils you use the magnetic field to push the electron field in the copper (not the electrons), as the field strengthens then weakens you get a wave effect in this field or to you and me a Pushing force (voltage). Its like a stick of wood is your magnetic field and if you push it through the water it creates a bow wave in front of it although not exactly the same it creates a visual context that might agree with you.

Finally something that makes sense....

so electrons never move in wires in ours homes either?

 

[telectrix]

well, they move, but don't go anywhere. they oscillate, causing a movement of the electron field. the theory is far too deep for forum discussions. think of this. the surface of the earth is rotating at anything up to 1000mph. why are we not flung off?